Torque transfer unit with integrated electric drive motor

ABSTRACT

An axle assembly comprises a power transmission device including a housing having a cylindrically shaped sidewall. The power transmission device selectively communicates rotatable motion from an input member to an output member. A frictional clutch is disposed in the housing and includes a drum. A first and a second axle shaft selectively drive a first and a second drive wheel, respectively. A differential selectively transfers drive torque from the output member to at least one of the first and second axle shafts. An electric motor comprising a coil and a plurality of magnets is provided on the axle assembly. In one example, the coil is disposed on the housing and the magnets are disposed on the drum. The coil is configured to selectively energize to provide one of a positive or negative torque input to the output member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/050,001 filed Mar. 17, 2011 (now U.S. Pat. No. 8,597,145 issued Dec.3, 2013), the disclosure of which is incorporated by reference as if setforth herein in its entirety.

FIELD

The present disclosure relates generally to a torque transfer unit withan integrated electric drive motor.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Due to increased demand for four-wheel drive and all-wheel drivevehicles, many power transmission systems are being incorporated intovehicle driveline applications for transferring drive torque to thewheels. Many vehicles include a power transmission device operablyinstalled between the primary and secondary drivelines. Such powertransmission devices are typically equipped with a torque transfermechanism for selectively transferring drive torque from the primarydriveline to the secondary driveline to establish a four-wheel drivemode of operation.

Some power transmission devices are operable for automatically directingdrive torque to the secondary wheels without any input or action on thepart of the vehicle operator. When traction is lost at the primarywheels, a clutch is actuated for transferring torque to the secondarywheels to establish the four-wheel drive mode. Some power transmissiondevices are equipped with an electrically-controlled clutch actuatoroperable to regulate the amount of drive torque transferred across theclutch to the secondary driveline as a function of changes in vehicleoperating characteristics such as vehicle speed, throttle position, andsteering angle. While many power transmission devices are currently usedin four-wheel drive vehicles, a need exists to advance the technology.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

An axle assembly comprises a power transmission device including ahousing. In some examples, the housing can have a cylindrically shapedsidewall. The power transmission device selectively communicatesrotatable motion from an input member to an output member. A frictionclutch is disposed in the housing and can be actuated to selectivelytransfer torque between the input member and the output member. Thefriction clutch includes a first clutch member and a second clutchmember. The first clutch member is operatively coupled to the inputmember while the second clutch member is operatively coupled to theoutput member. First and second axle shafts drive first and second drivewheels, respectively. A differential transfers drive torque from theoutput member to at least one of the first and second axle shafts. Anelectric motor comprising a coil and a plurality of magnets is providedon the axle assembly. In one example, the coil is disposed on thehousing and the magnets are disposed on the second clutch member. Thecoil can be selectively energized to provide one of a positive ornegative torque input to the output member.

According to other features, the first and second axle shafts are rearaxle shafts. The coil is arranged on the cylindrically shaped sidewallof the housing. The first clutch member is a clutch hub and the secondclutch member is a cylindrical clutch drum. The magnets are disposed onan outer cylindrical surface of the drum. The frictional clutch is a wetclutch.

According to other features, the power transmission device is configuredto operate in various drive modes. For example, the power transmissiondevice can operate in an electric motor assist drive mode wherein theelectric motor is energized and provides either a positive or negativetorque to the output shaft. The power transmission device is furtherconfigured to operate in an electric drive mode wherein the frictionclutch of the power transmission device is not coupled and wherein theelectric motor is energized and provides a sole torque input to theoutput shaft. The power transmission device is further configured tooperate in a regenerative drive mode wherein the electric motor providesa braking input to the power transmission device and wherein the brakinginput provides a regenerative input to a battery. According to oneexample, the differential is a rear differential.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

The present invention will become more fully understood from thedetailed description and the accompanying drawings wherein:

FIG. 1 is a cross-sectional side view of a power transmission deviceincorporating an electric motor and constructed in accordance to oneexample of the present teachings;

FIG. 2 is a schematic of a four-wheel drive vehicle equipped with thepower transmission device of FIG. 1 and shown in a first drive mode;

FIG. 3 is a schematic of a four-wheel drive vehicle equipped with thepower transmission device of FIG. 1 and shown in a second drive mode;

FIG. 4 is a schematic of a four-wheel drive vehicle equipped with thepower transmission device of FIG. 1 and shown in a third drive mode;

FIG. 5 is a schematic of a four-wheel drive vehicle equipped with thepower transmission device of FIG. 1 and shown in a fourth drive mode;

FIG. 6 is a schematic view of a four-wheel drive vehicle equipped withthe power transmission device of FIG. 1 and shown in a fifth drive mode;and

FIG. 7 is a cross-sectional side view of a power transmission deviceincorporating an electric motor constructed in accordance to otherfeatures of the present teachings.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings. The following description of the preferredembodiments is merely exemplary in nature and is in no way intended tolimit the invention, its application, or uses.

The present invention is directed to an axle assembly including a torquetransfer unit or power transmission device that may be adaptivelycontrolled for modulating the torque transferred between a rotatableinput member and a rotatable output member. The power transfer devicemay be useful within motor vehicle drivelines as a stand-alone devicethat may be easily incorporated between sections of propeller shafts,directly coupled to a drive axle assembly, or other in-line torquecoupling applications. Accordingly, while the present invention ishereinafter described in association with a specific structuralembodiment for use in a driveline application, it should be understoodthat the arrangement shown and described is merely intended toillustrate an exemplary embodiment of the present invention.

With initial reference to FIGS. 1 and 2 of the drawings, a drive train10 for a four-wheel vehicle is shown. Drive train 10 includes a firstaxle assembly 12, a second axle assembly 14, and a powertrain assembly16 for generating and delivering drive torque to the axle assemblies 12and 14, respectively. In the particular arrangement shown, the firstaxle assembly 12 is the front axle while the second axle assembly 14 isthe rear axle. The powertrain assembly 16 includes an engine 18 and amulti-speed transmission 20 having an integrated front differential unit22 for driving front wheels 24 via front axle shafts 26. The powertrainassembly 16 further includes a transfer unit 28 driven by thetransmission 20 for delivering torque to an input member 29 of a torquetransfer unit or power transmission device 30 via a drive shaft assembly32. The input member 29 of the power transmission device 30 is coupledto the drive shaft assembly 32 while its output member 31 is arranged todrive a rear differential 36. The second axle assembly 14 also includesa pair of rear wheels 38 that are connected to the rear differential 36via rear axle shafts 40.

The drive train 10 is shown to include an electronically-controlledpower transfer system 42 that includes the power transmission device 30.The power transfer system 42 is operable to selectively provide drivetorque in a two-wheel drive mode or a four-wheel drive mode. In thetwo-wheel drive mode, torque is not transferred via the powertransmission device 30. Accordingly, 100% of the drive torque deliveredby the transmission 20 is provided to the front wheels 24. In thefour-wheel drive mode, power is transferred through the powertransmission device 30 to supply drive torque to the rear wheels 38. Thepower transfer system 42 further includes a controller 50 that is incommunication with vehicle sensors 52 for detecting dynamic andoperational characteristics of the motor vehicle. The vehicle sensors 52can include, but are not limited to, sensors that can determine wheelspeed, wheel slip, steering wheel angle, yaw rate, throttle position,engine/transmission torque, vehicle speed, stability control status,etc.

The controller 50 is operable to control actuation of the powertransmission device 30 in response to signals from the vehicle sensors52. The controller 50 may be programmed with a predetermined targettorque split between the first and the second set of wheels 24 and 38,respectively. Alternatively, the controller 50 may function to determinethe desired torque to be transferred through the power transmissiondevice 30 via other methods. Regardless of the method used fordetermining the magnitude of torque to transfer, the controller 50operates the power transmission device 30 to maintain the desired torquemagnitude. As will become further appreciated from the followingdiscussion, the controller 50 may also communicate with an electricmotor 56 that is arranged on the power transmission device 30 forproviding positive or negative torque in various drive modes to assistin vehicle operation.

With specific attention now to FIG. 1, the power transmission device 30will be described in greater detail. The input member 29 is shown toinclude an input shaft 70 while the output member 31 is shown to includean output shaft 72. The output shaft 72 is preferably a pinion shafthaving a pinion meshed with a ring gear on the rear differential 36. Thepower transmission device 30 also includes a friction clutch 74 that isoperably dispersed between the input shaft 70 and the output shaft 72.The power transmission device 30 also includes a housing assembly 75that comprises a front housing 76 and a substantially cup-shaped rearhousing 78. The rear housing 78 can be supported on an axle carrier 80.The rear housing 78 includes a generally cylindrically shaped side wall82 that has an inner circumferential surface 84. The input shaft 70 issupported in the front housing 76 by a bearing 86. The output shaft 72is received by a tubular output spindle 88 that is supported in the rearhousing 78 by bearings 90 and 91.

The input shaft 70 includes a raised splined portion 92 defining aclutch hub 94. A set of inner friction plates 96 are drivingly coupledto the clutch hub 94 via a splined engagement. The inner friction plates96 are interleaved with a plurality of outer friction plates 98. Theouter friction plates 98 are in splined engagement with a clutch drum100. The drum 100 is generally cylindrically shaped and defines an innercavity 102 within which the interleaved friction plates are located. Thedrum 100 further includes an outer circumferential surface 103. Theouter circumferential surface 103 opposes the inner circumferentialsurface 84 of the side wall 82. The drum 100 is drivingly coupled to aradial flange portion of the output spindle 88. The output spindle 88 iscoupled for rotation with the output shaft 72 via another splinedinterface. In the embodiment depicted, the friction clutch 74 is a wetclutch. Accordingly, clutch fluid is contained within the cavity 102defined by the drum 100 and is in communication with the friction plates96 and 98. Fluid is also contained within the housing assembly 75.

A piston 104 is slidably positioned within a cavity 106 that is formedwithin the housing assembly 75. The piston 104 is axially movable intoengagement with a thrust bearing 108 and an apply plate 110. Pressurizedfluid can flow through a conduit 112 formed in the front housing 76 andact on a front face 114 of the piston 104. Other configurations arecontemplated. When pressurized fluid builds on the face 114 of thepiston 104, the piston 104 translates and applies a force through thethrust bearing 108 and the apply plate 110 to the plurality ofinterleaved clutch plates 96 and 98. Torque is transferred between theinput shaft 70 and the output shaft 72 via the components previouslydescribed when the friction plates 96 and 98 are forced into contactwith one another. A hydraulic powerpack 116 is schematically shown inFIGS. 1 and 2 and is arranged to provide a controllable source ofpressurized fluid to conduit 112. Regulation of the fluid pressure inconduit 112 acts to proportionally regulate the clutch engagement forceapplied by piston 104 to apply plate 110 which, in turn, regulates thedrive torque transferred from input shaft 70 to output shaft 72.Controller 50 is shown to communicate with hydraulic powerpack 116 andis operable to control the fluid pressure generated by the hydraulicpowerpack 116. While not limited thereto, the powerpack 116 can includea motor-driven fluid pump and valving for controlling the fluid pressuredelivered to conduit 112.

The electric motor 56 generally includes a plurality of magnets 120 anda coil 122. In the example shown, the magnets 120 are fixedly mounted onthe outer circumferential surface 103 of the drum 100 for concurrentrotation therewith. The magnets 120 can be a plurality of magnetsarranged around the outer circumferential surface 130 of the drum 100.In this regard, the magnets 120 can use the drum 100 as a rotor. Thecoil 122 is fixedly mounted onto the inner circumferential surface 84 ofthe rear housing 78. The electric motor 56 can therefore occupy a spacedefined by an annular pocket 126 defined generally between thecylindrically shaped side wall 82 of the rear housing 78 and the outercircumferential surface of the drum 100. The electric motor 56 canreceive power from an on-board battery source 130 and/or other powersources such as the vehicle's alternator. The coil 122 can be energizedto cause the magnets 120 and therefore the drum 100 to rotate in a firstdirection that corresponds to a forward rotation of the drive axle 14 ora second direction that corresponds to a reverse rotation of the driveaxle 14. It is appreciated that in some examples, as described herein,the resultant torque input from the electric motor 56 can supplement(positively or negatively) the drive torque already supplied by theengine 18 through the input shaft 70.

As will be described in the following discussion directed towards FIGS.2-6, the electric motor 56 adds functionality to the power transmissiondevice 30 and can be active or inactive in various drive modes. In thisregard, the controller 50 can, in addition to controlling actuation ofthe friction clutch 74, send a signal to the electric motor 56 toactivate and deactivate the electric motor 56 according to variousinputs from the vehicle sensors 52. It is contemplated that thecontroller 50 can be configured to automatically activate and deactivatethe electric motor 56 based on driving conditions or alternatively froma driver initiated input (i.e., drive mode selector switch, etc.).

As shown in FIG. 2, the power transmission device 30 is decoupled todefine a first drive mode. More specifically, the friction clutch 74 isnot engaged. In this regard, drive torque is not transmitted from theinput shaft 70 to the output shaft 72. In addition, the electric motor56 is inactive. With the power transmission device 30 operating in thefirst drive mode, the drive train 10 operates in a front wheel drivemode such that power is communicated only to the front wheels 24 via thepowertrain 16.

Turning now to FIG. 3, the power transmission device 30 is shown in asecond drive mode. In the second drive mode, the friction clutch 74 ofthe power transmission device 30 is at least partially engaged such thatdrive torque is transferred from the input shaft 70 to the output shaft72 to provide power to the rear wheels 38 through the rear differential36. In the second drive mode, the drive train 10 is operating in aconventional on-demand all wheel drive mode. In the second mode asillustrated in FIG. 3, the electric motor 56 is inactive.

Turning now to FIG. 4, the power transmission device 30 is shownoperating in a third or electric motor assist drive mode. In the thirddrive mode, the friction clutch 74 is at least partially engaged suchthat torque is transferred from the input shaft 70 to the output shaft72 such that the drive train 10 is operating in a conventional on-demandall wheel drive mode. In the third drive mode as shown in FIG. 4, theelectric motor 56 is also active. The electric motor 56 can provide apositive torque input to the drum 100 resulting in an increase in netdrive torque being transferred to the output shaft 72. In somecircumstances, the electric motor 56 can alternatively provide anegative torque onto the drum 100 such that a reduced output torque istransferred to the output shaft 72. In either scenario, the controller50 can communicate a signal to the electric motor 56 that correspondswith the desired positive or negative torque input.

With reference now to FIG. 5, the power transmission device 30 is shownin a fourth or electric drive mode. In the fourth drive mode, the powertransmission device 30 is inactive such that the friction clutch 74 isnot engaged and drive torque is not communicated from the input shaft 70to the output shaft 72. However, in the fourth drive mode, drive torquecan be communicated to the output shaft 72 solely from the electricmotor 56. In this regard, in the fourth drive mode, the controller 50can operate the power transmission device 30 in an electric on-demandall wheel drive mode where the front wheels 24 are provided drive torquefrom the engine 18 while the rear wheels 38 are provided drive torquesolely through the electric motor 56. Additionally, in the fourth drivemode, the controller 50 can operate the drive train 10 such that theonly wheels being supplied with drive power are the rear wheels 38 thatare powered solely from the electric motor 56.

With reference now to FIG. 6, the power transmission device 30 is shownoperating in a fifth or regenerative drive mode. In the fifth drivemode, the friction clutch 72 is disengaged such that drive torque is nottransmitted from the input shaft 70 to the output shaft 72. In the fifthdrive mode, the electric motor 56 can be used in a battery charge,regenerative mode. In this regard, the electric motor 56 can be used athigher vehicle speeds for braking while utilizing the braking input as aregenerative input to the battery 130. Additionally or alternatively,the electric motor 56 can be used at low vehicle speeds such as tomaintain a vehicle speed.

With reference now to FIG. 7, a power transmission device 230constructed in accordance to additional features of the presentteachings is shown. The power transmission device 230 includes similarfeatures as discussed above with respect to the power transmissiondevice 30. In this regard, similar components are identified withreference numerals increased by 200.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A torque transfer device comprising: a firsthousing; a second housing mounted to the first housing, the first andsecond housings cooperating to define a cavity; a first shaft receivedin the first housing and extending into the cavity; a plurality of firstclutch plates received in the cavity and non-rotatably coupled to thefirst shaft; a second shaft received in the second housing; an outerclutch drum mounted on the second shaft, the outer clutch drum beingreceived in the cavity and disposed about the first shaft; a pluralityof second clutch plates received in the cavity and non-rotatably coupledto the outer clutch drum, the second clutch plates being interleavedwith the first clutch plates to form a clutch pack; a first bearingmounted to the first shaft and the first housing, the first bearingsupporting the first shaft for rotation relative to the first housing,the first bearing being disposed on a first side of the clutch pack; asecond bearing mounted to the outer clutch drum and the second housing,the second bearing supporting the outer clutch drum for rotationrelative to the second housing, the second bearing being disposed on asecond side of the clutch pack such that the clutch pack is disposedaxially along a rotational axis of the first and second shafts betweenthe first and second bearings; an actuator configured to compress theclutch pack against the outer clutch drum to permit rotary power to betransmitted between the first and second shafts; and an electric motorhaving a stator and an armature, the stator being fixedly coupled to thefirst and second housings and received in the cavity, the armature beingcoupled to the outer clutch drum for common rotation.
 2. The torquetransfer device of claim 1, wherein the actuator is a hydraulicactuator.
 3. The torque transfer device of claim 2, wherein the firsthousing defines a piston chamber and wherein the actuator comprises apiston that is received in the piston chamber.
 4. The torque transferdevice of claim 1, wherein the outer clutch drum is supported by a thirdbearing that is disposed between the first shaft and the outer clutchdrum.
 5. The torque transfer device of claim 4, wherein the outer clutchdrum comprises a cylindrical projection that is received into anaperture formed in the first shaft.
 6. The torque transfer device ofclaim 1, further comprising a lubricating oil that is received in thecavity.
 7. The torque transfer device of claim 1, wherein the actuatorcomprises an apply plate, which is abutted directly against the clutchpack.
 8. The torque transfer device of claim 7, wherein the actuatorfurther comprises a thrust bearing that is abutted directly against theapply plate on a side of the apply plate that is opposite the clutchpack.
 9. A torque transfer device comprising: a housing assemblydefining a cavity; a first shaft received in the housing assembly andextending into the cavity; a plurality of first clutch plates receivedin the cavity and non-rotatably coupled to the first shaft; a secondshaft received in the housing assembly, the second shaft being a pinionshaft that is adapted to drive a pinion that is meshed with a ring gearof a differential mechanism; an outer clutch drum mounted on the secondshaft, the outer clutch drum being received in the cavity and disposedabout the first shaft; a plurality of second clutch plates received inthe cavity and non-rotatably coupled to the outer clutch drum, thesecond clutch plates being interleaved with the first clutch plates toform a clutch pack; an actuator configured to compress the clutch packagainst the outer clutch drum to permit rotary power to be transmittedbetween the first and second shafts; and an electric motor having astator and an armature, the stator being fixedly coupled to the housingassembly and received in the cavity, the armature being coupled to theouter clutch drum for common rotation.
 10. The torque transfer device ofclaim 9, wherein the actuator is a hydraulic actuator.
 11. The torquetransfer device of claim 10, wherein the housing assembly defines apiston chamber and wherein the actuator comprises a piston that isreceived in the piston chamber.
 12. The torque transfer device of claim9, wherein the outer clutch drum is supported on a bearing that isdisposed between the first shaft and the outer clutch drum.
 13. Thetorque transfer device of claim 12, wherein the outer clutch drumcomprises a cylindrical projection that is received into an apertureformed in the first shaft.
 14. The torque transfer device of claim 9,further comprising a lubricating oil that is received in the cavity. 15.The torque transfer device of claim 9, wherein the actuator comprises anapply plate, which is abutted directly against the clutch pack.
 16. Thetorque transfer device of claim 15, wherein the actuator furthercomprises a thrust bearing that is abutted directly against the applyplate on a side of the apply plate that is opposite the clutch pack.